Conventional method for enjoying three-dimensional images include a method of using a lens sheet whose surface has a lenticular lens having multiple cylindrical convex lenses arrayed in parallel (hereinafter, also referred to as a lenticular sheet) and a method called integral photography using a fly eye lens having multiple convex lenses arrayed in a plane.
These methods provide viewers with three-dimensional images by arranging images for a right eye and a left eye in corresponding positions of the multiple lenses, that is, parallactic images. Therefore, unless the parallactic images are arranged in correct positions corresponding to the lenses, no three-dimensional images are provided.
Accordingly, in order to locate parallactic images in the correct positions of the lenses, a technique is disclosed for printing parallactic images directly on a lenticular sheet (for example, refer to Patent Document 1). Another technique is disclosed for printing parallactic images in the corresponding positions of part of the lenses of a lenticular sheet left on the print surface (for example, refer to Patent Document 2).
In addition to the printing techniques disclosed in Patent Documents 1 and 2, the cost reduction of lenticular sheets and the spread of printers have allowed creators to easily print parallactic images on print media to generate three-dimensional images. Moreover, this allows not only the creators to view the parallactic images but also to send print media on which parallactic images are printed to other persons as postcards.
When the created lenticular sheets are sent as postcards, in such circumstances, the technique disclosed in Patent Document 1 requires writing an addressee on the lenticular sheet on which parallactic images are printed. When an addressee is written, the addressee is overwritten on the parallactic images. To prevent it, it is necessary to bond a sheet of paper such that overwritten addressee has no effect on the parallactic images onto the parallactic images with an adhesive while registering the paper with the lenticular sheet. For such bonding work, the creator must take care not to stain the parallactic-image printed surface or not to peel off the printed parallactic images. This will trouble the creator with a significant load.
The technique disclosed in Patent Document 2 can not print parallactic images on the lenticular lens left to the surface on which parallactic images are to be printed. Therefore, when the lenticular sheet is sent as a postcard, the whole surface of the postcard cannot be used for three-dimensional images.
[Patent Document 1] Japanese Patent No. 3471930
[Patent Document 2] JP-A-2005-196153